The present invention relates to an image input unit and an image input method for inputting a color image to be printed out.
Hitherto, in a printer, complementary color ink has been used to finally output image data representing the values of CMY (Cyan, Magenta, Yellow) or CMYK (Cyan, Magenta, Yellow, blacK) and in a monitor, image data representing the values of RGB (Red, Green, Blue) is finally output. Generally, in image processing using a computer, color matching is performed with the display colors of a monitor as the reference and therefore in an image input unit such as a digital still camera, image data is represented in the area of RGB color space with the RGB values taking 0 or more. For example, in not only a digital still camera using primary color CCD, but also a digital still camera using complementary color CCD, when CMYG (Cyan, Magenta, Yellow, Green) image data provided from an input image is converted into RGB image data, processing of adjusting the components of a conversion matrix or replacing negative values with 0 is performed and only RGB values of 0 or more are output.
For example, in sRGB standard, color coordinates of RGB are determined and RGB color space wherein the RGB values are 0 or more is defined. However, the sRGB color space is narrower than the color space that can be recognized by the visual sense of a human being and thus only a color space in a narrower range than the visual sense of a human being can be represented in an image input unit for outputting an image represented in the sRGB color space.
On the other hand, in a printer, a color space wherein the CMY or CMYK values are 0 or more can be represented by printing. A printer for outputting an image represented in the color space wherein the CMY or CMYK values are 0 or more can use pigments for color development on the outside of the sRGB color space as CMY ink, thereby representing a wider color space than the sRGB-defined color space by printing. Likewise, the printer can represent a wider color space by printing than a color monitor manufactured with sRGB display as the reference.
For such a printer to print image data recorded in an image input unit such as a digital still camera for recording an image represented in a color space wherein RGB colors represented in sRGB are 0 or more, the image is represented only in a narrower range than the color representation area of the printer, and the characteristics of the printer are not used effectively; this is a problem.
In recent years, image data format standards allowing negative values in the colors of sRGB64, RIMM-RGB, etc., have been developed. However, if an attempt is made to allow negative values and improve the image quality, the information amount per pixel is increased three bits and thus the image data formats result in an increase in the data capacity.